This project is aimed at the development of computational methods for the flow of blood in the heart with emphasis on the fluid dynamics of heart valves. We have developed a computer model of the left side of the heart which can be used as a test chamber in computational studies of the fluid dynamics of the natural mitral valve and in computer testing of prosthetic heart valves. We propose to use these methods to study mitral valve prolapse syndrome, the role of atrial systole in mitral valve closure, the fluid dynamics of straight and curved pivoting disc prosthetic mitral valves, and also the fluid dynamics of butterfly bileaflet valves. In the computational studies of prosthetic valves, our approach is to vary the parameters of the valve design and to observe the effect on predicted valve performance. This program of computer testing should complement more traditional methods such as tests in physical models, animal experiments, and clinical trials. The strengths of the computational approach are that the investigator has complete control over the conditions of the test, that the parameters of the valve design are easily varied, and that a wealth of detailed, quantitative information is available as output.